Cradle-type telephone subset



' K. w. NlLssoN CRADLE-TYPE TELEPHONE SUBSET June 22, 1948.-

Filed April 3. 1944 2 Sheets-Sheet 1 June 22, 1948. K. w. NlLssoNCRADLE-TYPE TELEPHONE SUBSET 2 Sheets-Sheet 2 Filed April 3, 1944Watentec-l `lune 22', 1948 2,443,799 CRADLE-TYPE TELEPHONE sUesE'r KarlWilhelm Nilsson, Stockholm, Sweden, as-

signor to Telefonaktiebolag'et L M Ericsson, Stockholm, Sweden, acompany of Sweden Application April 3, 1944, serial No. 529,317 InSweden June 2, 1943 2 Claims. f 1

The invention relates 'to telephone instruments in which the contactsprings arranged in the instrument are actuated by means or" two pinsmovably arranged in the cradle of the casing. In known instruments ofthis kind the motive mechanism between said pins and contact springsconsists of a bridge supported on a horizontal shaft, one part of thebridge being operated by the pins and the other part operating thecontact springs. Said shaft is thereby supported in a rack fixed toabase plate. Said motive mechanism which thus is composed of a number ofdetails causes a comparatively strong friction. Besides the frictionproduced in the supporting points of the bridge, friction is alsoproduced on account of the displacement of the point of application ofthe pins on the bridge and on account of lateral pressure on the pins,since the direction of the pressure acting between the bridge and thepins does not coincide with the longitudinal direction of the pins. Onaccount of the comparatively high friction the spring used to maintainthe bridge in an idle position must be powerfully built. Due to this theweight of the handset should not fall below a given value. As a lowweight of the handset is wanted, as small a friction as possible isdesirable.

'l'he invention has the object of providing a motive mechanism of saidkind having an exceedingly low friction and, moreover, being very simpleof design and easily mounted. The invention will described more indetail with reference to accompanying drawings which show an embodiment.

Fig. l is a cross section of the instrument. Fig. 2 is a side elevationof the contact springs. Fig. 3 is a cross section of a portion of theinstrument along the line A-A in Fig. 1, and Fig. 4 shows a portion ofthe base plate and the details mounted thereon.

I signifies the instrument casing, 2 and 3 are the pins movably arrangedin the cradle. The contact springs i are fixed to the base plate 6 bymeans of a bent plate 5. The shaft 'I is in one end riveted to the baseplate 6. A member 8 of insulating material in the shape of a cylindricalring provided with a bottom 22 and top and bottom bearings 9, lllenabling it to slide on the shaft l, is provided. Said member isperformed with stop surfaces I2, I3 for the pins 3, 2 and with awedge-shaped stud I8 which, on the movement of the member, operates thesprings 4. As a sufficient space between the bearings 9 and IB isdesired in order to secure a good guidance, but the height of the casingat the same time is placed above a plane running through the stopsurface I2, I3 and perpendicularly to the shaft 1.

Around the shaft 'l a coil-spring Il is arranged between the member iland the base plate 6 which spring tends to move said member and pins 2,i! to their upper position in which the stud I8 does not operate thesprings 4 and which position is taken up by said member when the handsetis lifted from the cradle. When the handset is restored the member 3 isdisplaced downwardly against the eiect of the spring II, the stud I8thereby actuating the springs Il.

The member 8 is centered in its vertical movement by cooperation betweenthe wedge I8 and the springs I9, 2li which are arranged with theirlongitudinal direction Vertical. In order to prevent that the member Sduring mounting or adjusting, when the casing is removed, isunintentionally turned, thereby injuring the springs, said member isprovided with an arm I4 which engages a guide I5 consisting of one legof the U-shaped plate 5 and having a hole IB, shaped as an hour-glass.At a correct adjustment of the springs I9, 2U no friction is causedbetween the arm lli and the guide I5 during the vertical movement of themember 8.

0n account of the design of the motive mechanism according to theinvention, i. e., a member slidable along a fixedly arranged shaft, thelongitudinal axis of which coincides with that of the pins, it has beenpossible firstly to considerably reduce the friction, thus enabling theuse of a light handset and, secondly, to simplify the manufacture andmounting of said motive mechanism. An instrument according to theinvention enables the use of a handset, the weight of which is 20% lessthan the weight of a handset used in hitherto known instruments. Theshaft may be made of raw material which need not be treated in any otherway than forming the one end into a tap which is then riveted to thebase plate. The member with its arms I2, I3, Iii and the stud I3 arecast in a single structure, for instance in Bakelite. The cylindricalshape of the member t is shown in the embodiment considerably simplifiesthe manufacture in case said member is pressed in Bakelite.

I claim:

1. In a cradle telephone having a removable handset, a casing, two pinspushed downwards when the handset is placed on the cradle and movedupwards when the handset is removed lfrom the cradle, contact springsoperated upon placing and removing of the handset, a shaft iixedlyarranged within said casing and disposed parallel with the pins, amember having the shape of a cylindrical ring of press-material, theaxis of which is perpendicular to said shaft, said' ring member beingsldably arranged on said shaft at two diametrically opposed points, saidmember being pushed down by means of said pins when the handset isplaced on the cradle, spring means for moving said member upwardly whenthe handset is removed from the cradle, and means on said member foroperating said contact springs upon movement of said member.

2. In a cradle telephone having a removable handset, a casing, two pinspushed downwards when the handset is placed on the cradle and movedupwards when the handset is removed from thel cradle, contact springsoperated upon` placing and removing of the handset, a shaft xedlyarranged within said casing and disposed parallel with the pins, amember having the shape of aV cylindrical ring of press-material, theaxis REFERENCES CITED The following references are of record in thefile-of this patent:

UNITED STATES PATENTS Number Name Date 1,917,724 Kvaal July 11, 19342,205,491 Puckette et al June 25, 1940

